Hydraulic oil will gear pump skeleton oil seal breakdown and overflow to produce oil seal string oil. Gear pump oil will seriously affect the normal operation of the machine. The reason, generally have the following four aspects. 1. Parts manufacturing quality is poor (1) the quality of the lip seal lip geometry failed, tighten the spring too loose, resulting in tightness test leaks, gear pump into the host easily after the breakdown of the oil seal and oil . Seal should be replaced and tested for material, geometry and size. (2) gear pump machining, assembly quality due to the gear pump processing, assembly quality problems, resulting in gear shaft rotation center and the front cover is not the center of the heart, resulting in partial eccentric seal. Check the symmetry and displacement of the bearing pin hole on the locating pin hole, the concentricity of the pinch seal at the front cover and the coaxiality of the bearing oil hole at the bearing hole (through hole). (3) sealing ring material and processing quality As a result of sealing ring material and processing quality problems, resulting in cracks and scratches the seal ring, resulting in the second seal is not strict or even failure, a lot of pressure oil into the frame seal (here for the low pressure channel ) Too late to return oil, resulting in oil seals were punctured and string oil. Should check the seal ring material and processing quality. (4) The external spline connection of the internal spline of the transmission spline shaft and the gear pump. And installed together in the loader, if the spline shaft concentricity over spun shaft processing, will make the rotation of different hearts, resulting in gear shaft swing, affect the seal seal, resulting in seal string oil. Should check and control the spline shaft, the concentricity of the external spline. 2. Gear pump and host installation quality requirements (1) Gear pump and host installation up to requirements Gear pump installed on the host, the requirements of its installation of the coaxial error is less than 0.05mm. If the transmission spline shaft installed on the spline shaft center of the beat beat tolerance, will make the gear pump in the high-speed rotation under radial load, resulting in the oil seal was broken and oil string; in particular the sleeve CBZb Pump, gear bearing radial pressure will destroy the radial compensation sleeve, the harm is much larger than the fixed gap type CBG gear pump. (2) The installation gap between the components does not require the gear pump front and rear pump cover and the pump port from the positioning effect, therefore, with the gap can not be too large; Gear pump external spline belongs to the transmission device, with the gap should not be too Small, otherwise it will form an interference. (3) Too thick asbestos pad between the front end face of the gear pump cover and the transmission assembly end During the installation process, the clamping force of the four fixing bolts is inconsistent, causing the pump to deflect, affecting the oil seal. Asbestos pad sealing sealant between the assembly end face, although the seal is more reliable, but to the maintenance of a lot of inconvenience, asbestos pad after the glue can only be used once. Whether it's a gear pump or a variable speed pump, replace the asbestos pad every time. It is recommended to use 0.6 ~ 0.8mm thick oil-resistant rubber pad, which can ensure the seal, the pump installation degree of bias is small, but also can be repeated multiple use, and can reduce vibration and noise. (4) spline rolling oil seal oil seal As the gear pump shaft spline and variable speed output shaft spline effective contact length shorter, while the gear pump torque transmission work is certain. Gear pump work sprocket to withstand high torque squeeze wear or even rolling key, resulting in high temperature, resulting in skeleton oil seal lip burn, aging, and then be punctured and oil. Therefore, the host should check the gear pump shaft spline gear strength, and to ensure that there is enough effective binding length. 3. The impact of hydraulic system cleanliness Hydraulic system by the tank, gear pumps, piping, control valves and hydraulic cylinders and other important components. Hydraulic system work, due to a variety of control valve for the injection molding forging, sticking to the internal sticky sand and other factors due to pressure oil and make it off the hydraulic system caused by pollution. At the same time, the fuel tank and pipe welding slag, hydraulic cylinder internal flash, burrs and other factors also contributed to the hydraulic system contaminated. After the hydraulic system is polluted, the friction between the gear pump and the gear will be aggravated, and the sealing effect will be caused. As a result, the gear pump oil seal will be punctured and oil will be knocked out. Therefore, to seriously carry out the body sand, fuel tank and hydraulic accessories and hydraulic cylinder cleaning, etc., in order to ensure the cleanliness of the hydraulic system. 4. The impact of hydraulic oil (1) hydraulic oil poor cleanliness, pollution particles big gear shaft journal and seal ring hole clearance is very small, contaminated particles into the seal ring will cause the inner hole wear, scratch or rotate with the shaft , Resulting in secondary seal pressure oil into the low pressure area (skeleton seal), resulting in oil seal was punctured. Should deal with poor cleanliness of the hydraulic oil filter or replace the new anti-wear hydraulic oil. (2) Viscosity of hydraulic oil will drop, the viscosity of deteriorating hydraulic oil will drop, the fluid will become thin after the deterioration, and the leakage through the secondary seal gap will increase under the condition of high pressure in the gear pump. Because it is too late to return the oil, High breakdown of oil seals lead to string oil. It is recommended to regularly test the oil, and replace the anti-wear hydraulic oil (L-HM46 ~ 68 GB11119-98).